Засолённые почвы Харамодонской низменности Баргузинской котловины

Abstract

In “humid” latitudes within the lacustrine-alluvial part of the Barguzin depression, azonal saline soils are widespread. Genesis of these soils is affected by a combination of endogenous (current seismic activity and tectonic disturbance at the intersection of Nizhneargadinskiy and Khaskhal-Argadinskiy faults, discharges of low mineralized waters) and exogenous factors (aridity in the spring-early-summer period, permafrost, cryogenic metamorphism). The study was performed at the area of Kharamodon lowland near saline lakes. The conjugate series of soils located on the bottom of a dried-up lake and in the contact zone of the transition from the lake-alluvial plain to the terrace of the Upper Kuitun terrain were investigated. The soils developed in the zone of tectonic faults with deep waters wedging are characterized by extremely high dynamics of soil forming conditions such as the contrasting combination of physical and chemical properties of soil horizons, heterogeneous texture, soda and sulfate-soda type of salinity, and geochemical peculiarities of the element associations. The salt crusts, humus-underdeveloped or light-humus diagnostic horizons with signs of aeolian stratification and gleying are the features of the morphological structure of these soils. Within the saline soil profiles, dark, almost black layers and turbations are noted, which are typical for soils of active tectonic faults zones with thermal low mineralized waters unloading. The concentrations, salts distribution, degree and type of chemistry in the soils under the study are sharply changed over a short distance. In the soils of accumulative positions, solonchaks with very high soda salinity entire the profile are formed. There is no vegetation due to the strong salt toxicity. In the layered-aeolian humus saline permafrost soil located in the contact zone of the transition from the lake-alluvial plain to the terrace, surface salinity with less toxic sulfate anion prevails (salt crust). Downhill soda-sulfate and sulfate-soda types occurred, sodium predominates among the cations. Halophilic and halotolerant plant species form the low projective cover (30%). The maximum content of easily soluble and toxic salts is concentrated in the salt crusts of the quasi-clay cryoturbated solonchak and in the layered-aeolian soil. Light-humus saline aeolian-stratified permafrost soils developed at the highest hypsometric levels are of weak degree of mixed type salinity of the upper horizons that favors vegetation growth. The latent discharge of mineralized waters affects the saline soils composition. In comparison with the clark of the Earth's lithosphere, accumulation of Ba2,5, Sr2,3, Ca1,8, Mg1,7, P1,6 is occurred. In the saline soils of the Haramodon lowland, not typical for the parent rocks elements such as Mg3,2, S2,9, Li2,3, P2,0, Co2,0, Ca1,8, Mn1,7, V1,6, Cu1,6, Cr1,6, Ti1,5, Ni1,5, Fe1,4 are accumulated.